Emperor penguin air sac oxygen

Some marine birds and mammals can perform dives of extraordinary duration and depth. Such dive performance is dependent on many factors, including total body oxygen (O2) stores. For diving penguins, the respiratory system (air sacs and lungs) constitutes 30-50% of the total body O2 store. To better understand the role and mechanism of parabronchial ventilation and O2 utilization in penguins both on the surface and during the dive, we examined air sac partial pressures of O2 (PO2) in emperor penguins (Aptenodytes forsteri) equipped with backpack PO2 recorders. Cervical air sac PO2s at rest were lower than in other birds, while the cervical air sac to posterior thoracic air sac PO2 difference was larger. Pre-dive cervical air sac PO2s were often greater than those at rest, but had a wide range and were not significantly different from those at rest. The maximum respiratory O2 store and total body O2 stores calculated with representative anterior and posterior air sac PO2 data did not differ from prior estimates. The mean calculated anterior air sac O2 depletion rate for dives up to 11 min was approximately one-tenth that of the posterior air sacs. Low cervical air sac PO2s at rest may be secondary to a low ratio of parabronchial ventilation to parabronchial blood O2 extraction. During dives, overlap of simultaneously recorded cervical and posterior thoracic air sac PO2 profiles supported the concept of maintenance of parabronchial ventilation during a dive by air movement through the lungs.

部分海鸟与海洋哺乳动物可完成时长与深度均远超常规的潜水行为。此类潜水能力受多种因素影响，其中包括机体总氧（O2）储备。对于潜水企鹅而言，其呼吸系统（气囊与肺）占机体总氧储备的30%~50%。为深入理解平行支气管通气（parabronchial ventilation）与氧利用在企鹅静息状态及潜水过程中的作用机制，本研究对搭载背负式氧分压（PO2）记录仪的帝企鹅（Aptenodytes forsteri）的气囊氧分压展开了检测。静息状态下的颈气囊氧分压低于其他鸟类，而颈气囊与后胸气囊之间的氧分压差更大。潜水前的颈气囊氧分压通常高于静息状态，但波动范围较广，且与静息状态下的数值无显著差异。通过代表性的前气囊与后气囊氧分压数据计算得到的最大呼吸氧储备与机体总氧储备，与此前的估算结果并无差异。时长不超过11分钟的潜水活动中，前气囊的平均氧消耗速率约为后气囊的十分之一。静息状态下较低的颈气囊氧分压，可能源于平行支气管通气与平行支气管血液氧摄取率的比值偏低。潜水过程中，同步记录的颈气囊与后胸气囊氧分压曲线存在重叠，这一结果支持了“潜水期间通过肺部气流维持平行支气管通气”的假说。